<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <img id="h1" src="img/off.gif"> <br><br>

    <div class="cls">传智教育</div> <br>
    <div class="cls">黑马程序员</div> <br>

    <input type="checkbox" name="hobby"> 电影
    <input type="checkbox" name="hobby"> 旅游
    <input type="checkbox" name="hobby"> 游戏
</body>
<script>
    //1. 点亮灯泡 : src 属性值
    //获取img标签对象
    var img=document.getElementById("h1");
    img.src="img/on.gif";


    //2. 将所有div标签的内容后面加上: very good (红色字体) -- <font color='red'></font>
    var divs=document.getElementsByTagName("div");
    for(let i=0;i<divs.length;i++){
        const div=divs[i];
        div.innerHTML+="<font color='red'>very 666</font>";
    }

    //3. 使所有的复选框呈现选中状态
    var ins=document.getElementsByName("hobby");
    for(let i=0;i<ins.length;i++){
        const check=ins[i];
        check.checked=true;
    }

</script>

</html>